Stanley Coren

The lateral preference inventory for measurement of handedness, footedness, eyedness, and earedness: Norms for young adults

The Lateral Preference Inventory is a brief, 16-item questionnaire, which validly measures hand, foot, eye, and ear preference. Normative data is presented for 3,307 subjects, ranging in age from 17 to 35 years. Data is separated by sex, since females are found to be more right-sided than are males for hand, foot, and ear. Data are presented in a format that should allow various scoring and coding criteria to be applied. These norms could serve as a reference or control comparison for measures of laterality taken on clinical or other targeted groups. A copy of the inventory appears in the Appendix.

LEFT-HANDEDNESS : A MARKER FOR DECREASED SURVIVAL FITNESS

Life span studies have shown that the population percentage of left-handers diminishes steadily, so that they are drastically underrepresented in the oldest age groups. Data are reviewed that indicate that this population trend is due to the reduced longevity of left-handers. Some of the elevated risk for sinistrals is apparently due to environmental factors that elevate their accident susceptibility. Further evidence suggests that left-handedness may be a marker for birth stress related neuropathy, developmental delays and irregularities, and deficiencies in the immune system due to the intrauterine hormonal environment. Some statistical and physiological factors that may cause left-handedness to be selectively associated with earlier mortality are also presented.

Effect of Non-Target Stimuli upon Length of Voluntary Saccades:

The length of initial voluntary saccades to a target were measured in three experiments. It was found that saccade length varied as a function of the number, locus and distance of non-target stimuli present in the visual field. Eye movements tended to be directed toward the “center of gravity” of the stimuli close to the target. These systematic changes seem to be independent of task requirements for acuity. Some implications are discussed.

A behaviorally validated self-report inventory to assess four types of lateral preference

Abstract A self-report battery for the assessment of hand, eye, foot and ear preference, which has been validated against behavioral tasks designed to measure the same four types of laterality, is presented. Data showing the concordance between the inventory and the behavioral tests for a sample of 171 individuals is given. The mean degree of concordance between the behavioral and the questionnaire items was 90%. Additional analyses revealed that both forms of measurement provide similar descriptions of both individual and population lateral preference patterns. This report offers the questionnaire battery as a convenient and useful tool for the measurement of the four most common indices of laterality.

An Efferent Component in the Visual Perception of Direction and Extent

After outlining the history of motor theories of visual perception, a new theory linking information extraction patterns, specifically adapted for the guidance of eye movements, to the visual perception of direction and extent is presented. Following a brief discussion of comparative and physiological considerations, a research strategy to test for efferent involvement in visual perception in humans is presented. In seven demonstration experiments, predictions from efferent considerations are used to create a new set of illusions of direction and extent and to demonstrate new predictable variations in the magnitude of some classical illusion figures. Another demonstration illustrates that systematic changes in visual perception occur as a function of changes in motoric demands, even in the absence of any configurational changes in the stimulus. A final section shows the relationship between attention and efferent readiness and their interaction in the formation of the conscious visual percept. From a historical perspective, most contemporary theories of visual perception are quite conservative. This conservatism springs from an apparent acceptance of the premise that any proper analysis of visual experience must avoid reference to nonvisual mechanisms, except for labeling and semantic aspects of the perceptual process. It follows that most visual theorists tend to derive virtually every aspect of the conscious percept solely from either the physical characteristics of the visual stimulus array or the operation of readily definable neurological units in the visual system. Characteristic of the former viewpoint is Gibsons (1979) theory of ecological optics, which maintains that virtually all aspects of the final percept are predictable from invariants in the stimulus array. Current attempts to derive the conscious percept from a hypothesized Fourier analysis occurring within the visual system are similar in approach, merely relying on higher

Environmental factors in hand preference formation: Evidence from attempts to switch the preferred hand

We surveyed 650 young adults to assess both their current handedness behaviors and past attempts to shift their hand preference. We found that 73 (11.2%) individuals had experienced hand preference change attempts and 52 (8.0%) had undergone pressure to switch hand preference to the right. The likelihood that an individual had experienced pressure to change hand use was not related significantly to gender or to a number of familial factors. However, the success of the hand change varied with gender; females reported greater success in shifting their handedness.

The Creation and Reversal of the Müller-Lyer Illusion through Attentional Manipulation:

A configuration is presented in which both the overestimated and the underestimated portions of the Müller-Lyer illusion are embedded. In free viewing no distortion of length occurs; however, overestimation or underestimation illusions can be produced by simple manipulation of the attentional set, thus demonstrating one cognitive component in the formation of the Müller-Lyer distortion.

Size contrast as a function of figural similarity

Size contrast occurs in numerous configurations where a test figure appears apparently larger when surrounded by small elements and apparently smaller when surrounded by large elements. Using the Ebbinghaus illusion, the magnitude of this effect is shown to vary as a function of apparent similarity between test and inducing element.

Size contrast as a function of conceptual similarity between test and inducers

In four experiments, the effect of the semantic relationship between test and inducing stimuli on the magnitude of size contrast in an Ebbinghaus-type illusion was explored. In Experiments 1 and 2, the greatest illusion was found when test and inducing stimuli were identical in shape and differed only in size. Decreased size contrast was found when inducing stimuli were drawn from the same category as the test stimulus, but were not visually identical. Even less size contrast was found when inducing stimuli were from a near conceptual category, with the least effect when they were drawn from a completely different category. In Experiment 3, it was demonstrated that even if test and inducing stimuli are drawn with identical geometric elements, the size contrast illusion is greatly reduced if they represent apparently different conceptual categories (through the manipulation of orientation and perceptual set). In Experiment 4, any geometric or spatial confounds were ruled out. These results suggest that size contrast is strongly influenced by the conceptual similarity between test and inducing stimuli.

Prediction of insomnia from arousability predisposition scores: Scale development and cross-validation

Abstract In light of evidence which suggests that some forms of insomnia may result from cognitive hyperarousal, an attempt was made to develop an instrument composed of items which measure arousability as a predisposition or a trait, in the hope that this might predict tendencies toward disrupted sleep patterns. Starting with an original pool of 314 items a 70 item preliminary inventory was selected. Next a sample of 196 subjects was used to develop and validate a 12-item self-report inventory called the Arousal Predisposition Scale. Item selection was based on the ability to predict a global measure of insomnia. The resultant scale was then cross-validated on a sample of 693 subjects and shown to be both a valid and reliable predictor of several indexes of sleep disturbance.